Method for the production of a catching connection in a linear drive

ABSTRACT

A method of providing a linear drive with an axially play-free entrainment connection between at least one linearly travelling rod ( 5 ) and a guide unit able to be moved parallel thereto. Between a coupling member ( 26 ), projecting to the fore of the rod ( 5 ), of the guide unit and the terminal face ( 27 ) of the rod ( 5 ) adhesive ( 34 ) is applied and then the components are so screwed together that athwart the direction of displacement relative motion is still possible. Then the entire unit is shifted between its two terminal positions even prior to curing of the adhesive ( 34 ), the components then aligning themselves. After the adhesive is cured the screw connection is finally drawn tight.

The invention relates to a method for the production of an axiallyplay-free entrainment connection between at least one rod mounted forlinear movement and a guide unit adapted to slide linearly inparallelism to it in linear drive, a coupling member of the guide unitbeing adhesively bonded to the rod and extending to the fore of an endface of the rod when the entrainment connection has been produced.

FIELD OF THE INVENTION

A linear drive as disclosed in the European patent publication 0868965B1 comprises at least one drive rod able to be shifted in relation tothe housing, such rod being kinematically coupled in a manner free ofaxial play with a guide unit also linearly sliding on the housing. Forthe connection with the drive rod the guide unit possesses a couplingmember designed as a yoke part, which extends to the fore of the driverod and is connected with it in a manner free of play in the axialdirection in order to produce an entrainment connection. Owing to shapeand positioning inaccuracies of the individual components theapplication of a draw force to the attachment screw transverse forcesmay arise, which impair the parallelism of the drive rod and the guideunit, something which may result in stiff running of the drive rod andthe guide unit and in increased wear and a reduction in the servicelife. A similar arrangement is disclosed in the German patentpublication 101 16 634 C2.

BACKGROUND OF THE INVENTION

In the case of a linear drive disclosed in the German patent publication(utility model) DE 20316693 U1 an attempt was made to tackle the abovementioned problems by not having a screw connection and replacing it bya-plain adhesive join. More particularly when tensile forces are to betransmitted this design however reduces the load carrying capacity ofthe linear drive.

The possibility of joining together two parts by an adhesive joint isdescribed in the textbook “Der Stirlingmotor, einfach erklaert undleicht gebaut” by Dieter Viebach, first edition 1998, published byOekobuch Verlag, Staufen bei Freiburg, pages 3, 4, 37 and 51. The bookexplains that a hub to be secured in a flywheel by means of atwo-component adhesive may be aligned in the flywheel as long as thetwo-component adhesive is not set.

One object of the present invention is to propose measures by which,while dealing with the wear problems render possible an entrainmentconnection with a high load carrying capacity within the force flow pathof the movement unit of a linear drive.

SUMMARY OF THE INVENTION

This aim is to be achieved in the present invention in conjunction witha method of the type initially mentioned in as far as that after theapplication of the adhesive the coupling member is screwed by means ofat least one attachment screw in such a manner axially to the rod thatrelative movements between the coupling member and the rod remainpossible athwart the direction of displacement, that then even prior tocuring of the adhesive the movement unit comprising the guide unit andthe rod is displaced axially at least once between its two stroke endpositions in relation to the housing of the linear drive, and that aftersubsequently curing of the adhesive the final screwing tight of theattachment screw is performed.

In this fashion the components to be connected are fixed in relation toeach other so that during the following operation of tightening the atleast one attachment screw there is no deflection of the components tobe screwed.

Accordingly there is a connection which is both free of axial play andcan resist heavy loads without making the guides present any stiffer.Prior to the curing of the adhesive exact alignment between the guideunit and the rod is achieved by at least one and preferably multiplereciprocations of the movement unit between the ends of the stroke, thepreliminary fixation performed in this context ensuring the necessaryaxial entrainment owing to the at least one attachment screw without therelative transverse mobility of the components, required for mutualalignment, being reduced.

The method may be employed both when the end of the rod to be coupledwith the guide unit and also when in this respect it is a question of adrive rod with for example—in the case of a fluid operated lineardrive—with one drive piston or—in the case of electrically activateddrive means.

Further advantageous developments of the invention are defined in thedependent claims.

The adhesive may readily be applied to a joint face, facing the rod, onthe coupling member, which is not peripherally limited. As moreparticularly of interest however a design is preferred in which thejoint face turned toward the rod, of the coupling member is provided onthe floor of a recess, into which the rod may fit and into which theadhesive has previously been applied.

In the following account the invention will be explained with referenceto the accompanying drawings.

LIST OF THE SEVERAL VIEWS OF THE FIGURES

FIG. 1 is a perspective representation of a linear drive produced usingthe method in accordance with the invention.

FIG. 2 shows the linear drive in accordance with FIG. 1 in alongitudinal section taken on the line II-II.

FIG. 3 shows the part marked III in FIG. 2 on a larger scale.

DETAILED ACCOUNT OF WORKING EMBODIMENT OF THE INVENTION

The linear drive 1 figured by way of example possesses a housing 2,wherein at least one linearly extending receiving space 3 is located inwhich a drive piston 4 is able to run linearly. A drive rod 5, which isconnected with the drive piston 4 and for instance by a screw thread,extends from the drive piston 4 in an axial direction and preferablythrough an end plate 6 in the form of a cover, into the surroundings.The drive piston 4 together with the drive rod 5 constitutes a driveunit 7 whose longitudinal axis 8 coincides with the longitudinal axis ofthe drive rod 5.

The drive piston 4 divides up the receiving space 3 axially into twoworking chambers 12 a and 12 b to each of which a separate fluid duct 13extends (which runs through the housing) in order to selectively feed apressure medium, for example compressed air, or to vent it andaccordingly to move the drive unit 7 in a linear movement 14 asindicated by a double arrow.

The drive rod 5 is in the illustrated working example hollow andaccordingly tubular in form. However it may consist of a solid material.Instead of a design involving fluid power for a drive force the lineardrive may also be powered electrically. In this case an electric motor15, indicated in chained lines, may be arranged on the housing 2 anddrivingly coupled with the drive rod 5 by drive means 16, for example bya lead screw.

By suitable design of the drive means the linear drive may also bedesigned in the form of an electrodynamic linear direct drive. In thiscase the drive forces are transmitted magnetically to the drive rod.

The terminal wall 6 is provided with a guide bushing 17 through whichthe drive rod 5 extends in order to produce a smooth running slide guidefor it.

A transverse support function for the drive rod 5 in relation to thehousing 2 at its inner end in the receiving space is performed by thedrive piston 4, which at its outer periphery is preferably provided withat least one guide ring 18, which is able to slide along the bore of thereceiving space 3.

Externally on the housing 2 a guide unit 22, which in the example isdesigned in the form of a carriage, is guided for linear sliding motion.The linear movement, which the guide unit 22 performs in relation to thehousing 2, will be termed the second linear movement 23 and is indicatedin FIG. 2 by a double arrow. Its direction is parallel to the directionof the first linear movement 14 of the drive unit 7.

A preferably table-like guide section 25 of the guide unit 22 extendsalongside the housing 2, the housing 2 overlapping the housing 2 inaccordance with its current position axially to a greater or lesserextent. At an end side of the guide section 25 a coupling member 26,preferably in the form of a yoke plate, is arranged, which extendsathwart the longitudinal axis 8 to the fore of the terminal face 27 ofthe terminal section, which is outside the housing 2, of the drive rod5.

The sliding support of the guide unit 22 is provided by a linear guidemeans 24 arranged between the guide section 25 and the housing 2. In theworking embodiment this means includes a central guide rail 28 which isflanked at the edge by two external guide rails 32 applied externally tothe housing 2, a suitable number of plain and/or anti-friction bearingelements being provided between the central guide rail 28 and eachexternal guide rail 32. The longitudinal axis 33 of the linear guidemeans 24 extends parallel to the longitudinal axis, coinciding with thelongitudinal axis 8, of the receiving space 3.

The drive unit 7 is kinematically coupled with the guide unit 22 in theaxial direction, that is to say in the direction of the linear movements14 and 23 free of play. For this purpose a axially play-free entrainmentconnection is provided between the drive rod 5 and the coupling member26 in front of it. The latter is in the form of a combination of anadhesive join and screw attachment. More details on this will begathered from the representation of FIG. 3 on a larger scale.

The drive rod 5 has its terminal face 27 resting on a face section(termed the joint face 35) of the coupling member 26 with theinterposition of a layer of adhesive 34. The adhesive 34 ensures in thiscase an intimate material connection between the above mentionedcomponents.

In order to produce the additional screw connection the drive rod 5possesses a threaded hole 36, opening at its terminal face and which ismore particularly coaxial, into which the shank 37 of an attachmentscrew 38 is screwed, which extends through an axially directed opening42 in the coupling member 26 from the side facing away from the driverod 5. The head 43 of the attachment screw 38 engages support face 44,directed axially away from the drive rod 5, of the coupling member 26 sothat on tightening the attachment screw 28 the drive rod 5 and thecoupling member 26 are braced onto the sandwiched adhesive 34.

Preferably the support face 44 is located in a recess in the couplingmember 26 receiving the full height of the screw head 43.

If by suitable actuation the first linear movement 14 of the drive unit7 is caused in the one or other direction there will be, on theapplication of a thrust or a pull, a transmission of force on the guideunit 22, which accordingly synchronously performs the second linearmovement 25. The latter may be transferred from the guide unit 22 inorder to for example shift or position a component of a machine, agripper employed for handling parts or some other component. For thedetachable fixing of component the guide unit 22 is provided withsuitable attachment means 45, for example in the form of threaded holes.

In order to ensure the lowest possible wear rate during operation of thelinear drive 1 the two linear movements 14 and 23 should be in exactparallelism. If the screw connection between the coupling member 26 andthe drive rod 5 were to be produced without additional measures the pullmoment then applied would however impair the parallel running of the twolinear movements 14, something which would entail stiff running in thelinear guide means 24 and at the guide bushing 17 and the guide ring 18.Accordingly the orderly, skew-free movement would not be possible, moreparticularly in the case of linear drives with a small overall size.Furthermore there would be more wear.

The linear drive in the example is in fact also manufactured using aparticular method, which renders possible complete transmission of forcewith the aid of a screw connection while simultaneously ensuring smoothrunning in operation.

In this method of manufacture the linear drive may be completelyassembled exclusive of the production of the entrainment connectionbetween the drive rod 5 and the coupling member 26. After a series ofproduction steps there is therefore a linear drive 1, in which both thedrive unit 7 and also the guide unit 22 are arranged in a linearlyadjustable manner on the housing 2, though not having any entrainmentconnection so that there is independent mobility.

After this adhesive 34 s applied on the terminal face 27 of the driverod 5 and/or on the joint face 35 of the coupling member 26 and then thetwo faces are thrust together by a force in opposite directions actingon the guide unit 22 and the drive unit 7.

In the next step the attachment screw 38 is introduced from the outsidethrough the opening 42 and screwed into the threaded hole 36. It istightened a little so that the adhesive connection between the couplingmember 36 and the drive rod 5 remains intact, despite simultaneousrelative movement athwart the shift direction of the drive rod 5 and theguide unit 22 between such components. This possibility of motion can,as shown in FIG. 3 by arrows, mean that the components may be shifted orpivoted in relation to each other.

In this preliminarily secured position held by the attachment screw 38the entire movement unit 46 comprising the guide unit 22 and the driveunit 7 is shifted once or several times between its two terminal strokepositions in relation to the housing 2. This preferably takes place bythe action of force from the outside on the guide unit 22, eithermechanically or manually.

This movement, called the alignment movement, of the movement unit 46,takes place before the adhesive 34 is cured or hardened. Accordingly theguide unit 22 and the drive unit 7 may be exactly aligned in relation toone another in accordance with the directions of the set first andsecond linear movements 14 and 23.

After completion of the alignment movement the system is left aloneuntil the adhesive 34 is cured. Such curing may occur relativelyrapidly, if for example a suitable two component adhesive or anultraviolet cured adhesive is utilized.

Once the adhesive is in fact cured, it will undertake the function of afilling or compensation composition supporting the drive rod 5 inrelation to the guide unit 22 and holding it fixedly in position, evenwhen later the attachment screw 38 is tightened with the necessarytorque for the transmission of force required for operation. It isaccordingly now possible to finalize the screw connection without anydanger of the drive rod 5 and the coupling member 26 losing theirrelative positions owing to a possible irregularity as regards theterminal face 27 and the joint face 35.

FIG. 3 now shows a final state, the guide face 35 and the terminal face27 being slightly oblique in relation to each other—somethingrepresenting the optimum state for the system in the example—thesandwiched adhesive maintaining such alignment despite any pull force inview of the attachment screw 38.

In the working embodiment on its side facing the drive rod 5 thecoupling member 26 is smooth and preferably continuously even in itsconfiguration. The joint face 35 cooperating with the terminal face 27or, respectively, the adhesive 34 is therefore not peripherally limitedso that the applied adhesive, which during the alignment movement may besqueezed out, may flow away.

On the one hand it may be an advantage to secure the adhesivemechanically in a certain fashion after application thereof. If it isdesired, on the side facing the drive rod 5 the coupling member 26 maybe provided with a recess 47 concentric to the opening 42, into whichthe terminal side of the drive rod 5 may be inserted a little and whosefloor represents the joint face 35. Such an alternative design isindicated in FIG. 3 in chained lines.

The method as explained may not only be employed in order to align adrive rod in relation to a guide unit 22. In a like fashion a guide rodcould be joined with a guide unit, even the guide unit itself being ableto have a guide rod as a guide section, which is then able to beconnected in accordance with the invention by way of a yoke-likecoupling member with the other guide rod and/or possibly even with anadditional drive rod.

The screw connection may instead of only one attachment screw 38 have aplurality of attachment screws, if the diameter of the rod to beconnected permits this.

1. A method for the production in a linear drive of an axially play-freeentrainment connection between at least one rod mounted for lineardisplacement and a guide unit adapted to slide linearly in parallelismto the rod, a coupling member of the guide unit extending to the fore ofan end face of the rod and being adhesively bonded to the rod when theentrainment connection has been produced, wherein, after the applicationof the adhesive, the coupling member is screwed by means of at least oneattachment screw in such a manner axially to the rod that relativemovements between the coupling member and the rod remain possibleathwart the direction of displacement, and wherein, even prior to curingof the adhesive, a movement unit comprising the guide unit and the rodis shifted axially at least once between its two stroke end positions inrelation to a housing of the linear drive, and wherein, after thefollowing curing of the adhesive, the final screwing tight of theattachment screw is performed.
 2. The method as set forth in claim 1,wherein a shank of the attachment screw is inserted through an openingin the coupling member and screwed into a threaded hole in the rod, suchhole opening at a terminal face of the rod.
 3. The method as set forthin claim 1, wherein a joining face facing the rod is provided at thefloor of a recess, rendering possible insertion of the end of the rod,in the coupling member into which recess the adhesive is introduced. 4.The method as set forth in claim 1, wherein a peripherally limited facesection of the coupling member is provided as a joining face facing therod.
 5. The method as set forth in claim 1, wherein the movement unit isreciprocated several times between its stroke end positions prior tocuring of the adhesive.
 6. The method as set forth in claim 1, whereinat least one rod is constituted by a drive rod of the linear drive. 7.The method as set forth in claim 1, wherein said linear drive is drivenby fluid force or electrically.
 8. The method as set forth in claim 1,wherein said guide unit is designed carriage-like.
 9. The method as setforth in claim 1, wherein said coupling member is in the form of a yokeplate.